Class: EnvironmentConfigTransmogrifier

Inherits:
BaseTransmogrifier show all
Defined in:
lib/environment_config_transmogrifier.rb

Overview

EnvironmentConfigTransmogrifier uses environment variables to generate config values for specific keys.

Defined Under Namespace

Classes: NoEscapeMustache

Constant Summary collapse

@@memoize_mustache = 
{}

Class Method Summary collapse

Methods inherited from BaseTransmogrifier

inject_value

Class Method Details

.extend_replace(hash, path) ⇒ Object 



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# File 'lib/environment_config_transmogrifier.rb', line 88

def self.extend_replace(hash, path)
  # This code assumes that 'path' points to a directory of files.
  # The name of each file is the key into the hash, and the contents
  # of the file are the value to enter, as-is. The order of the
  # files in the directory does not matter.
  Dir.glob(File.join(path, '*')).each do |file|
    key   = File.basename(file)
    value = File.read(file)

    # Write the collected information to the hash. This will
    # overwrite, i.e. replace an existing value for that name. This
    # means that the values found in 'path' have priority over the
    # values already in the 'hash'. This is what we want for
    # '/etc/secrets'
    hash[key.upcase.tr('-', '_')] = value
  end
end

.mustache_message_from_error(error) ⇒ Object 



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# File 'lib/environment_config_transmogrifier.rb', line 73

def self.mustache_message_from_error(error)
  lines = error.message.split(/\n/)
  return 'No reason for failure given by mustache library' if lines.empty?
  return lines.first if lines.size < 4

  caret_line = lines[3]
  caret_pos = caret_line.index('^')
  return lines[0] + '.' unless caret_pos

  delimiter = '{{=(( ))=}}'
  actual_line = lines[2]
  leading_junk = actual_line.lstrip.start_with?(delimiter) ? actual_line.index(delimiter) : 0
  lines[0] + ": Error at or near position #{caret_pos - leading_junk} of template value."
end

.process_mustache_template(value, input_hash, key) ⇒ Object 



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# File 'lib/environment_config_transmogrifier.rb', line 56

def self.process_mustache_template(value, input_hash, key)
  val = @@memoize_mustache.fetch(value, {})[input_hash]
  return val if val

  delimiter = '{{=(( ))=}}'
  begin
    mustache_value = NoEscapeMustache.render("#{delimiter}#{value}", input_hash)
    # replace new lines with double new lines for proper new-line YAML parsing
    mustache_value = mustache_value.to_s.gsub("\n", "\n\n")
    @@memoize_mustache[value] ||= {}
    @@memoize_mustache[value][input_hash] = YAML.safe_load(mustache_value)
  rescue StandardError => e
    msg = mustache_message_from_error(e)
    raise LoadYamlFromMustacheError, "Could not load config key '#{key}': #{msg}"
  end
end

.transmogrify(base_config, environment_templates, secrets: nil) ⇒ Hash

Processes the mustache templates and injects new keys into the configuration

Returns:

  • (Hash) —

    Hash containing the updated configuration



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# File 'lib/environment_config_transmogrifier.rb', line 26

def self.transmogrify(base_config, environment_templates, secrets: nil)
  # build input hash for mustache
  input_hash = ENV.to_hash

  # load secrets
  extend_replace(input_hash, secrets) if secrets && File.directory?(secrets)

  # remove empty values
  input_hash.reject! { |_, v| v.nil? || v.empty? }

  # iterate through templates
  environment_templates.each do |key, value|
    # generate value from template

    # we need to process the template at least once, even if it doesn't
    # actually contain a mustache template, to get value types correctly;
    # by default, all values are strings, because they come from the environment
    # we need to unmarshall them using YAML.load
    loop do
      value = process_mustache_template(value, input_hash, key)
      break unless value.respond_to?(:include?) && value.include?('((')
    end

    # inject value in huge json
    inject_value(base_config, key.split('.'), value, key)
  end

  base_config
end